Towards fault-seal characterization in carbonate-dominated reservoirs: a proposed stochastic workflow

While there is an established industry workflow for fault-seal characterization in siliciclastic reservoirs, no similar workflow exists for fault-seal characterization in carbonate-dominated reservoirs, despite significant proportions of the Earth's oil and gas resources being trapped in that type of reservoir. The established workflow relies on fault clay content prediction to estimate key fault rock properties (capillary threshold pressure and permeability). However, this workflow is typically not applicable to carbonate-dominated reservoirs, partly because they usually have low clay contents and partly because of variability due to processes of fracturing, cementation and diagenesis during fault-rock development. The following principles are used as the basis for developing a workflow for fault-seal characterization in carbonate-dominated reservoirs: Fault properties are likely to have significant variability over short-length scales, and as a result, are inherently difficult to predict deterministically. Therefore, a stochastic approach capturing the uncertainty in a long-fault property variability is likely to be preferable. Intrinsic properties such as host rock porosity and permeability will have a strong influence on the fault rock properties. Different cross-fault juxtaposition types will have different fault properties and will also have different levels of fault property variability. Fault displacement does not have a strong influence on fault properties but does influence their continuity, and this will need to be accounted for in any proposed workflow. The proposed workflow presented in this paper is outlined and demonstrated for both exploration and field development and/or production problems on a synthetic data set.